Function analysis of RNase E in the filamentous cyanobacterium Anabaena sp. PCC 7120

In the filamentous cyanobacterium, Anabaena sp. PCC 7120, single heterocysts differentiate at semi-regular intervals in response to nitrogen stepdown. HetR is a principal regulator of heterocyst differentiation, and hetP and hetZ are two genes that are regulated directly by HetR. In a hetR mutant generated from the IHB (Institute of Hydrobiology) substrain of PCC 7120, heterocyst formation can be restored by moderate expression of hetZ and hetP. The resulting heterocysts are located at terminal positions. We used a tandem promoter, PrbcLPpetE, to express hetZ and hetP strongly in the hetR mutant. Co-expression of hetZ and hetP enabled the hetR mutant to form multiple contiguous heterocysts at both terminal and intercalary positions. Expression of hetZ, alone resulted in terminally located heterocysts, whereas expression of hetP, alone produced enlarged cells in strings. In the absence of HetR, formation of heterocysts was insensitive to the peptide inhibitor, RGSGR.

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Early candidacy for differentiation into heterocysts in the filamentous cyanobacterium Anabaena sp. PCC 7120

Archives of Microbiology ◽

10.1007/s00203-009-0525-4 ◽

2009 ◽

Vol 192 (1) ◽

pp. 23-31 ◽

Cited By ~ 18

Author(s):

Masakazu Toyoshima ◽

Naobumi V. Sasaki ◽

Makoto Fujiwara ◽

Shigeki Ehira ◽

Masayuki Ohmori ◽

...

Keyword(s):

Filamentous Cyanobacterium ◽

Cyanobacterium Anabaena ◽

Anabaena Sp ◽

Pcc 7120

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An increase in the level of 2-oxoglutarate promotes heterocyst development in the cyanobacterium Anabaena sp. strain PCC 7120

Microbiology ◽

10.1099/mic.0.26462-0 ◽

2003 ◽

Vol 149 (11) ◽

pp. 3257-3263 ◽

Cited By ~ 43

Author(s):

Jian-Hong Li ◽

Sophie Laurent ◽

Viren Konde ◽

Sylvie Bédu ◽

Cheng-Cai Zhang

Keyword(s):

Inorganic Nitrogen ◽

Cell Types ◽

Filamentous Cyanobacterium ◽

Nitrogen Status ◽

Gene Encoding ◽

Combined Nitrogen ◽

Cyanobacterium Anabaena ◽

Anabaena Sp ◽

Pcc 7120 ◽

Heterocyst Development

In the filamentous cyanobacterium Anabaena sp. strain PCC 7120, a starvation of combined nitrogen induces differentiation of heterocysts, cells specialized in nitrogen fixation. How do filaments perceive the limitation of the source of combined nitrogen, and what determines the proportion of heterocysts? In cyanobacteria, 2-oxoglutarate provides a carbon skeleton for the incorporation of inorganic nitrogen. Recently, it has been proposed that the concentration of 2-oxoglutarate reflects the nitrogen status in cyanobacteria. To investigate the effect of 2-oxoglutarate on heterocyst development, a heterologous gene encoding a 2-oxoglutarate permease under the control of a regulated promoter was expressed in Anabaena sp. PCC 7120. The increase of 2-oxoglutarate within cells can trigger heterocyst differentiation in a subpopulation of filaments even in the presence of nitrate. In the absence of a source of combined nitrogen, it can increase heterocyst frequency, advance the timing of commitment to heterocyst development and further increase the proportion of heterocysts in a patS mutant. Here, it is proposed that the intracellular concentration of 2-oxoglutarate is involved in the determination of the proportion of the two cell types according to the carbon/nitrogen status of the filament.

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